Ricerc@Sapienza

The research was focussed on the effects of cadmium (Cd) and arsenic (As), alone or combined, on Arabidopsis
post-embryonic roots, with attention to quiescent centre formation and development in relation to auxin
homeostasis. To the aim, morphological and histochemical analyses were carried out on seedlings, exposed or
not to Cd and/or As, of wild type, and transgenic lines useful for monitoring quiescent centre identity, auxin
localization and cellular influx and efflux. Moreover, auxin levels and expression of the YUC6 auxin biosynthetic
gene were monitored in Cd and/or As exposed wild type seedlings. Results showed that Cd and Cd plus As
increased the lateral and adventitious root density, whereas As alone reduced it. In the lateral and adventitious
root apices Cd and/or As negatively affected quiescent centre identity and auxin localization, changed auxin
levels, expression of YUC6, and of PIN1 and LAX3, auxin efflux and influx carriers, respectively. The alteration in
auxin homeostasis was different for the two pollutants, explaining their contrasting response on the post-embryonic
roots.